Reversible causes of cardiac arrest (PEA / asystole) — tick each cause as the team considers and addresses it.
H's
Hypovolemia
Hypoxia
Hydrogen ion (acidosis)
Hyper-/hypokalemia
Hypothermia
T's
Tension pneumothorax
Cardiac tamponade
Toxins
Thrombosis — pulmonary (PE)
Thrombosis — coronary (MI)
Evidence
Original publication
Panchal AR, Bartos JA, Cabañas JG, Donnino MW, et al. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. The Adult Cardiac Arrest Algorithm directs identification and treatment of reversible causes — the H's and T's — during resuscitation for pulseless electrical activity and asystole.
Circulation, 2020
Open source
Last reviewed: 2026-09
Report an error in this calculator
MedScore is an educational and clinical decision-support tool. It does not provide a diagnosis, a treatment, or a drug-dosing recommendation, and it does not replace clinical judgement or local guidelines. Confirm every result against the original source before acting on it. The treating clinician remains responsible for all decisions.